A statistical method for quantifying the field effects of urban heat island mitigation techniques

Abstract

The Lowry approach (1977) sets the framework for evaluating the meteorological effects of the urban heat island (UHI), by describing it as the superposition of "background", "local" and "urban" climates. In this paper, by adapting this framework to the study of UHI countermeasures, we propose a statistical method suited for assessing their effects in the field. The framework demonstrates that direct comparisons between case and control sites cannot isolate the impacts of UHI countermeasure. It also shows that the interstation differences before and after countermeasure implementation cannot be considered as statistically independent. Consequently, statistical procedures suited for handling dependent observations are necessary such as a linear mixed or fixed effects model. As a case study, experimental data from pavement-watering experiments conducted in Paris since 2013 are used, with the goal of assessing its cooling effects for two different watering strategies. With the fixed effects model, long-lasting statistically-significant effects are found. Results indicate beneficial thermal effects for pedestrians with reductions of UTCI-equivalent temperature up to 2°C, and duration of statistically-significant effects directly linked to the watered surface area. The method is limited by the number of measurements that must be gathered both before and after the UHI countermeasure implementation.

Experimental and Numerical Analysis on a Thermal Barrier Coating with Nano-Ceramic Base: A Potential Solution to Reduce Urban Heat Islands?

“…Had we focused on surface temperatures in various urban areas, we might have obtained divergent observations regarding this index, with conclusions akin to those derived from our experimental analyses; notably, that the HE-HR-TBC significantly reduces surface temperatures in urban environments. In our case, the deliberate choice of the UTCI as a metric stems from the intention to achieve the most accurate possible representation of the impact of Urban Heat Islands on individuals, like in several other studies [54,68,69].…”

Analysis of the heat budget of standard, cool and watered pavements under lab heat-wave conditions

“…Other methods also exist, such as pavement-watering (Hendel et al 2016, Kinouchi & Kanda 1997, Takahashi et al 2010, Yamagata et al 2008, Azam et al 2018, implemented for instance by the City of Paris since 2013 through experimental summer campaigns using the supply of the city's non-potable water network. The method was found to reduce the UTCI-equivalent temperature at pedestrian height up to 3°C during the day despite the increase in relative humidity up to a few percent (Hendel et al 2016, Parison et al 2020a). The study further highlighted the influence of the type of material being watered on the performance of the process.…”